1. Field of the Invention
The invention relates to a medical guide wire provided to assist a catheter when inserting it into a somatic cavity to cure or examine a diseased area (e.g., vascular stenosis area) and used to measure the diseased area.
2. Description of Related Art
In a medical guide wire which introduces a leading distal end into a diseased area through a sinuous vascular system, the leading distal end of the medical guide wire is inserted into the blood vessel or the somatic cavity by a “push-pull and turn” manipulation at a hand access portion located outside a subject patient upon treating the diseased area.
In order to achieve a smooth manipulation when inserting the leading distal end into the somatic cavity and the blood vessel, the medical guide wire requires multi-mechanical properties. The multi-mechanical properties are represented by a high flexibility, a good straightness and an improved restitutivity from a bending deformation. The medical guide wire of this type requires high flexibility at its leading distal end, while at the same time, appropriate rigidity is required at its rear portion. It is also indispensable for the leading distal end to have a high maneuverability in which the leading distal end properly responds to the hand operation which is to be done outside the subject patient.
As shown in FIG. 14, a medical guide wire 20 has basically an elongated and flexible front end portion 21A which has a diameter-increased hand access portion 22B and a tapered-off front end 22A of the core member 22. A helical spring 23 is secured to both ends of the tapered-off front end 22A.
With the basic structure of FIG. 14 in mind, Japanese Laid-open Patent Application No. 2001-178829 discloses a reverse blood stream stop means provided as an annular weir between an inner circumference of the helical spring 23 and the front end 22A of the core member 22 so as to prevent the reverse blood stream from entering into the helical spring 23 through gaps appeared between coil lines of the helical spring 23.
Japanese Laid-open Patent Application No. 8-173547 discloses a connection securement between an inner circumference of the helical spring 23 and an outer circumference of the front end 22A of the core member 22 so as to prevent the front end 22A from being inadvertently broken due to a stress concentration.
Japanese Domestic Laid-open Patent Application No. 7-500749 discloses radiopaque markers M as shown in FIG. 15. The radiopaque markers M are secured to an outer circumference of the tapered-off front end 22A with an annular space provided between the markers M and the helical spring 23. Alternatively, the markers M are secured to an inner circumference of the helical spring 23 with an annular space provided between the markers M and the front end 22A of the core member 22. The markers M enable a manipulator to measure the diseased area upon inserting the guide wire into the somatic cavity while projecting the radiation rays against the markers M.
The reverse blood stream stop means, the connection securement and the radiopaque markers M are placed within a space which is provided inside the helical spring 23. This negatively affects the bending characteristics upon inserting the front end portion 21A into a sinuous or tortuous path within the somatic cavity, or guiding the front end portion 21A selectively into one of the bifurcated portions of the blood vessel. This also negatively affects the steerability when implementing the “push-pull and turn” manipulation at the hand access portion located outside the subject patient upon treating the diseased area.
Therefore, it is an object of the invention to overcome the above drawbacks so as to provide a high quality medical guide wire which contributes to curing a diseased area with a good performance.